Aerogels are porous solids with high surface areas that are made by forming a gel network and removing the solvent without causing pore collapse. Due to characteristics such as high surface area, high porosity, and low density, these lightweight aerogels are attractive for use as thermal insulators, low dielectric substrates, catalyst supports, and as building and construction materials.
The most common class of aerogels is silica aerogels. Silica aerogels are extremely fragile and moisture sensitive. As a result, the utility of monolithic silica aerogels is limited to a few exotic applications such as thermal insulation to protect the Warm Electronics Boxes (WEB) onboard the Mars Exploration Rovers from the extreme temperatures present in the Martian environment for an extended period of time. Silica aerogels were also implemented in the aerogel collection grid, a panel comprised of an array of silica aerogel, deployed as a part of the Stardust spacecraft in January 2004. Polyimide aerogels are a relatively new category of aerogels which possess superior mechanical properties to the silica aerogels. However, in their current form, polyimide aerogels undergo dramatic thermally induced shrinkage at temperatures of just 150° C. Shrinkage results in densification of the aerogel as well as a change in pore size and shape which negatively impacts its insulation characteristics. Shrinkage reduces porosity and increases density, thus, increasing thermal conductivity. This drastically limits the scope of the use of polyimide aerogels, especially in scenarios where the insulation would experience elevated temperatures for extended periods of time.